Method and apparatus for helically winding strip material



Sept. 2, 1969 A. ZUBAL. ETAL 3,464,101

METHOD AND APPARATUS FOR HELICALLY WINDING STRIP MATERIAL Filed March30, 1967 I5 sheets sheet l FIGZ FlGl

STOCK HEAD STOCK THEIR ATTORNEY.

Sept. 2,1969 A, UBAL ETAL 3,464,101

METHOD AND APPARATUS FOR HELICALLY WINDING STRIP MATERIAL Filed March30, 1967 I 3 Sheets-Sheet 2 INVENTORS ANTHONY ZUBAL, HARRY F. DAVIS,

BY AM) M THEIR ATTORNEY.

Sept. 2, 1969 A. ZUBAL ETAL 3,464,101

rmaon AND APPARATUS FOR HELICALLY wmnms STRIP MATERIAL Filed March 30.1967 3 Sheets-Sheet 5 FIG.7

INVENTORS'.

ANTHONY ZUBAL,

HARRY F. DAVIS,

B-Y Ki j THEIR ATTORNEY.

United States Patent 3,464,101 METHOD AND APPARATUS FOR HELICALLYWINDING STRIP MATERIAL Anthony Zubal, Latham, and Harry F. Davis,Amsterdam,

N.Y., assignors to General Electric Company, a corporation of New YorkFiled Mar. 30, 1967, Ser. No. 627,109 Int. Cl. B2ld 11/06 US. Cl.29157.3 Claims ABSTRACT OF THE DISCLOSURE Gripping mechanism to forcecontinuous thin metal strip through an arcuate path defined by a shoe.Resulting spiral of strip is continuously applied to the outer surfaceof a rotating-translating cylindrical tube.

Background of the invention This invention relates to a method andapparatus for helically winding a continuous thin metal strip, and morparticularly, to a method and apparatus for helically winding acontinuous thin metal strip around the outer surface of a tube to form aheat exchanger element.

US. Patents 3,062,267 and 3,283,399, issued to Benjamin F. Hart andRoland P. Carlson, disclose a method and apparatus for helically windingstrip material. In the apparatus shown in those patents, the stripmaterial is motivated through the winding mechanism by the positiveaction of clutching members of the mechanism abutting against teethextending from the strip material. In the patents there shown, the stripmaterial is generally core iron and is wound in the form of a cylinder,the aforementioned teeth ultimately defining armature slots for thestators of dynamoelectric machines.

In the present invention, the strip material to be helically wound iscontinuous and uniform with no teeth extending therefrom. One effect ofthis is to create a need for a method of motivating the strip throughthe winding mechanism different from the prior art just discussed.

An additional feature of the present invention is that the helicallywound strip is continuously applied around the outer surface of acylindrical tubing which is continuously fed through the apparatus.

In the art of finned tubing manufacture, the process is typicallyperformed by a rotating tube pulling around itself an edgewise disposedstrip material. The strip is usually guided and set in place by one ormore grooved rollers. An example of this can be seen in US. Patent No.2,988,628Hall, particularly in FIGURES 3 and 4. This winding methodgives rise to localized stresses in the strip material. These stressescan cause buckling at the inner diameter of the resulting fin andstretching or tearing at the outer diameter if the fin is too high. Thatis, the strip material must be kept below a certain limiting width if itis to be applied by this prior art method.

By means of the present invention, the strip material is gripped at manypoints uniformly and urged into a helical configuration around a tube.This method and means greatly reduces the localized stressesaforementioned and permits wider strips of a soft material such ascopper to be wound around tubing to form higher and improved fins.

It is an object of the present invention to provide an improved methodand apparatus for the edgewise continuous winding of strip material on atubular workpiece.

Another object is to provide a clutching mechanism to motivate a stripmaterial through a helical winding mechanism.

Other objects, advantages and features of the present invention willbecome apparent from the following de- Patented Sept. 2, 1969 icescription when taken in connection with the accompanying drawing.

Summary of the invention Briefly, the method of the present invention ispracticed by motivating a continuous strip material through an arcuatepath about one of its edges and continuously applying the same to arotating tube which is moving axially through the aperture of thearcuate path of th strip. The result is a continuous spiral applicationof strip to tubing. The apparatus of the present invention includes aheadstock having an axial passage for tubing. A tailstock is operativelyconnected to the tubing and is movable in an axial direction pulling therotating tubing through the headstock. A clutch member with drive pinsindents and clutches strip material which is introduced transversely tothe axis of the tubing. The strip material is forced into an arcuatepath and applied edgewise to the rotating-translating tubing to form ahelical finned heat exchanger tube.

Drawing In the drawing:

FIG. 1 is a schematic of the environment of the present invention,

FIG. 2 is a perspective view of the edgewise strip winding mechanism ofthe present invention,

FIG. 3 is an exploded view of the operating members shown in FIG. 2,

FIG. 4 is a sectional view of the driving head of the present invention,

FIG. 5 is a perspective view of a single drive pin used in the drivinghead,

FIG. 6 is a view taken along the line VIVI of FIG. 3,

FIG. 7 is a front view of the cam member, and

FIG. 8 is a front view of the face of driving member in association witha strip-workpiece.

Description Referring to FIG. 1, the environment of the presentinvention is shown schematically to include a machine bed 1, a headstock 3 and a movable tail stock 5. A tubular workpiece 10 is mountedrotatably and translatably by means such as tail stock 5 operativelymounted on bed 1.

Referring now to FIG. 2, a driving head, generally indicated at 2, isshown in operative relationship to a stationary mounting frame 4 whichis part of head stock 3, an anvil or shoe 6, and a strip or workpiece 8.A tubular workpiece 10 is fed through frame 4 and driving head 2 with auniform axial velocity imparted to it as by tail stock 5. Driving head2, which is rotatable relative to frame 4 clutches strip workpiece 8,which is being fed transversely to tube workpiece 10, and pulls thestrip 8 up around the rotating and translating tube 10 resulting in acontinuous spiral of constant pitch of the strip 8 around and abuttingthe tube 10. The means by which strip 8 is clutched and motivated aroundtube 10 is the subject of the present invention and will now bedescribed in greater detail.

Referring now to FIG. 3, an exploded view is shown of the driving head2, frame 4, and anvil or shoe 6. Driving head 2 includes a shaft portion12 with an enlarged head portion 14 mounted integral therewith. Bothshaft portion and head portion are cylindrical having a cylindricalpassage or aperture through their centers for the accommodation oftubular workpiece 10. Head portion 14 has a plurality of axiallydirected holes 16 passing therethrough and circumferentially spaced anequal distance from the axis of head 14. The abutment of shaft portion12 to head portion 14 of the driving head 2 interferes with the clearpassage of holes 16 (see FIG. 4) for a purpose to be described.

Referring now to FIG. 5, a single drive pin 18 is shown in perspective.Drive pin 18 has a pointed tip 20 on one end thereof, which tip isrectangular or elongated in cross section. On the opposite end of drivepin 18 from. tip 20, a shoulder is formed by the removal of material sothat pin 18 extends through hole 16 and outward there from over theinterfering abutting shaft member 12. Mounted in this fashion, it willbe apparent that drive pin 18, while revolvable with head member 14, isnonrotatable relative to head member 14.

Referring again generally to FIGS. 3 and 4, stationary frame 4 is shownand is fixedly mounted on a machine tool bed 1. Frame 4 defines acylindrical hole in which driving head 2 is mounted rotatably. Anannular cam member 22 is fixedly mounted relative to frame 4. Cam 22 hasan axially facing cam surface 24. Cam surface 24 is in direct contact'with pin 18, though the drawing, for the sake of clarity, shows aslight clearance between the two members. In practice, there typicallywill be a ball thrust bearing between rotatable head member 14 andnonrotatable cam member 22. This too is left out of the drawing for thesake of clarity.

In FIG. 7, showing a front view of cam member 22, the cam surface 24 isshown as consisting of segments A and B. Segment A is slightly depressedrelative to segment B. At point 26, the transition from the highersegment B to the lower segment A is shown and is approximately 90 inadvance of transition 28 from segment A to segment B. The cam surface 24at segment B is axially displaced relative to segment A by a dimensionof the order of .004 inch.

Referring now to FIG. 6, the anvil or shoe member 6 is shown as itappears looking in the direction of movement of tube 10. Shoe 6 definesan aperture 30 which is coaxial with the aperture in driving head 2.Shoe 6 also has a guide or way 32 machined therefrom which extends fromthe edge of shoe 6 in a direction perpendicular to the axis of aperture30 and tangential thereto. Guide 32 follows the aperturecircumferentially around shoe member 6, for approximately 180. Shoe 6also has a radially extending projection 34 which extends inward towardaperture 30. Projection 34 is substantially a wedge-shaped member incross-section having a relatively pointed edge at its upper portion.

FIG. 8 shows a frontal view of the driving head 2 in its relation to theshoe 6 and the strip or workpiece 8 being fed thereto. Lines 260 and 28aare shown as phantom lines to correspond with transition lines 26 and 28in FIG. 7 which represent the transition portions of cam surface 24.

The operation of this machine will now be described. Assume as astarting point the presence of a suitable heat exchanger tube 10 passingthrough the aperture 30 of driving head 2 and shoe 6, such a tube beingoperatively connected to a tail stock by which the tube is rotated andtranslated. Concurrently, a continuous strip material is fed into theguide 32 of shoe 6 in a direction generally perpendicular to thedirection of movement of tube and tangential to the tube member itself.

As driving head 2, with its shaft 12 and head 14, retates relative toframe 4 and cam surface 24, drive pins 18 are actuated by the camsurface. As seen in FIGS. 6 and 8, when the head 14 rotates in acounterclockwise direction as shown, pins 18 are driven forward into thestrip material 8 at a point corresponding to point 28 on the camsurface. When the pins 18 are in this forward position, they grip stripmaterial 8 by the positive action of their tips 20. Rotating head 2 withtips 20 thus grip and pull the strip material 8 around a path defined bythe guide 32 of shoe 6. Approximately 270 following point 28 on the camsurface, transition point 26, the cam surface recedes so as to permitpins 18 to recede into the holes 16. The pins 18 are so motivated torecede into their holes by the inclined planar surface of projection 34.The pins are thus in a retracted position between points 26 and 28 (onthe cam surface) during the rotation of the head 14. As each pin againpasses point 28, it is forced forward to repeat the gripping action onstrip material 8. As pins 18 release the strip material 8 at point 26,the strip material emerges from shoe 6 on the downstream side ofprojection 34.

The pins 18 move forward only about .004 so as to clutch, but notpuncture, strip 8. Furthermore, pins 8 are nonrotatable relative to head14 so that the broad side of tips 20 are always doing the clutching.This, of course, provides stronger clutching action.

Since tube member 10 is constantly moving forward and rotating by meansof the tail stock 5, it will be seen that the continuously winding strip8 is wound edgewise around and abutting the tube in a helicalconfiguration relative thereto. The tail stock motor applying torque tothe tube 10 keeps the strip material 8 taut around the tube. The stripmaterial 8 which is thus helically wound edgewise around strip of tube10 may then be pulled through a straightening fixture to straighten outthe material if necessary. The strip is then brazed or welded to thetube. These latter processes are not material to the present invention.

The present invention enables the strip material 8 to be wound aroundtube 10 on its edge without the benefit or without the necessity of apreformed foot or flange on strip 8. The effect of this is a greateroverall diameter of tube 10 and strip 8 than could be obtained if strip8 were required to be bent into a flanged configuration.

It will be apparent that the invention herein described provides animproved method and apparatus for the edgewise helical winding of stripmaterial around tubing for the production of heat exchanger tubes.

It may occur to others of ordinary skill in the art to makemodifications of the present invention which will remain within theconcept and scope thereof and not constitute a departure therefrom.Accordingly, it is intended that the invention be not limited by thedetails in which it has been described but that it encompass all withinthe purview of the following claims.

What is claimed is:

1. A mechanism for winding continuous strip material in helicaldisposition around a tube, said mechanism comprising:

means to impart rotational and translational motions to a tubularworkpiece,

means to introduce said strip material in a direction substantiallynormal to the direction of translation of said tubular workpiece andsubstantially tangential to said tubular workpiece, and

means external to said tubular workpiece to motivate said strip materialaround a helical path to continuously surround and edgewise abut saidtubular workpiece,

said last named means including a revolvable circumferential array ofaxially movable drive pins having pointed tops arranged so as to indentand clutch said strip material on one surface thereof and cam means toactuate said drive pins into and out of their gripping position.

2. A mechanism for winding continuous strip material edgewise in helicaldisposition around a tube, said mechanism comprising:

means to impart rotational and translational motions to a tubularworkpiece,

a driving head defining an axial aperture for the passage therethroughof said tubular workpiece,

said driving head rotatably mounted relative to a fixed cam member onone end thereof and to a fixed shoe member on the opposite end thereof,

said shoe member defining a circular helical guide path around saidaperture,

said driving head defining circumferentially spaced coaxial holes inwhich are supported axially slidable drive pins having pointed tips,

said pins disposed in abutting relation to said cam member and beinglonger than said holes,

rotation of said driving head relative to said cam and said shoeimparting a reciprocating motion to said drive pins so that when saidstrip material is introduced to said guide path, said pointed tips ofthe clutching said strip material concurrently at a pludrive pins indentand clutch said strip on one surrality of surface locations.

face thereof and continuously motivate the same through said guide patharound and in edgewise abutting relation to said tubular workpiece. 103. A winding mechanism as defined in claim 2 in which said drive pinsare forced by said cam member into their References Cited UNITED STATESPATENTS c 2,374,144 4/1945 Stikeleather 29-1573 positions duringapproxlmately 270 of their 2,398,172 4/1946 gg 72 701 X 2 604 138 7/1952Harrison 29-157 3 X 4. A Wmdlng mechamsm as defined in claim 2 in which15 3062267 11/1962 H t l 72 172 said reciprocating motion has anamplitude of under .010". 3152629 10/1964 g zg ;6 X 5. A method forhellcally winding thin strip material 3,206,964 9/1965 Hart et a1 29 605X of uniform cross-section around the outer surface of a tube, saidmethod comprising the steps of:

concurrently rotating and translating a tubular work- 2 piece through afin winding mechanism, said fin winding mechanism including a pluralityof gripping members having pointed tips, introducing said strip materialto said fin winding mechanism in a direction substantially normal to the0 JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Assistant ExaminerU.S. Cl. X.R.

